1. Field of the Invention
The embodiments discussed herein are related to a semiconductor device, a metal member, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
A semiconductor device such as, for example, a semiconductor module conventionally has a configuration having a semiconductor chip, other components, and the like bonded by solder to a conductive plate on the surface of an insulating substrate. A device has been proposed as the semiconductor module, whose conductive plate and an external electrode terminal are electrically connected to each other by fitting an external electrode terminal into a hollow-tube metal member (hereinafter, referred to as “tubular contact member”) that is bonded by solder to the conductive plate on the front face of the insulating substrate (see, e.g., US Patent Publication No. 2009/194884). In US Patent Publication No. 2009/194884, the external electrode terminal and the tubular contact member are firmly fitted with each other by setting the largest dimension of the bottom face of the external electrode terminal to be slightly greater than the diameter of the hollow portion of the tubular contact member.
The configuration of the tubular contact member and the external electrode terminal of the conventional semiconductor module will be described. FIG. 12 is a cross-sectional diagram of a configuration of main portions of the conventional semiconductor module. FIG. 13 is a plan diagram of the configuration of the main portions of the conventional semiconductor module. FIG. 13 depicts the planar shapes of the hollow portion 104 and the external electrode terminal 125 of the tubular contact member 110 as viewed when a main body tube portion 101 of the tubular contact member 110 of FIG. 12 is cut along a cutting plane XY orthogonal to the central axis of the main body tube portion 101 and a multi-layered substrate 120 is viewed from the cutting plane XY. FIGS. 12 and 13 respectively correspond to FIGS. 14 and 12 of US Patent Publication No. 2009/194884.
As depicted in FIGS. 12 and 13, the tubular contact member 110 includes the hollow-tube main body tube portion 101, and flanges 102 and 103 respectively disposed on both of open ends 110a and 110b of the main body tube portion 101. The flange 102 of the first open end 110a of the tubular contact member 110 is bonded by solder (not depicted) to a conductive plate 122 of the front face of the multi-layered substrate 120. The multi-layered substrate 120 is formed by disposing the conductive plate 122 using copper (Cu) foil on the front face of a ceramic substrate 121 and disposing a sheet of copper foil 123 on the back face of the ceramic substrate 121. The tubular contact member 110 is electrically connected to a semiconductor chip 124 through the conductive plate 122 and a wire not depicted.
One end of the external electrode terminal 125 protrudes from a through hole 127 of a case 126 to outside of the case 126. The other end of the external electrode terminal 125 is fixed by being pressed into the main body tube portion 101 (the hollow portion 104) of the tubular contact member 110, to be fitted into the tubular contact member 110. The external electrode terminal 125 is electrically connected to the semiconductor chip 124 through the tubular contact member 110. The external electrode terminal 125 has a substantially square columnar shape and the largest dimension (the length of the diagonal line) d102 of the bottom face is slightly greater than the inner diameter (the diameter of the hollow portion 104) d101 of the main body tube portion 101 of the tubular contact member 110 (d101<d102). The planar shape of the main body tube portion 101 of the tubular contact member 110 is slightly deformed to match the shape of the bottom face of the external electrode terminal 125.
The following problem however arises with the conventional semiconductor module having the configuration depicted in FIGS. 12 and 13 where the external electrode terminal 125 is pressed into the main body tube portion 101 of the tubular contact member 110 to fit the external electrode terminal 125 therein. FIGS. 10, 11A, and 11B are schematic cross-sectional diagrams of states during manufacture of the conventional semiconductor module. FIG. 10 depicts an example of defective soldering attributable to the solderbility (the soldering property) when the tubular contact member 110 is soldered to the multi-layered substrate 120. FIGS. 11A and 11B depict an example of defects occurring when the external electrode terminal 125 is pressed into the main tube portion 101 of the tubular contact member 110.
As depicted in FIG. 10, when the flange 102 of the first open end 110a of the tubular contact member 110 is bonded by solder 128 to the multi-layered substrate 120, the solder 128 climbs up to an inner wall 110c of the main body tube portion 101 due to capillary action. In this case, the solder 128 tends to climb up the inner wall 110c of the main body tube portion 101 depending on the shape of the hollow portion 104 of the tubular contact member 110. According to a method of soldering the multi-layered substrate 120 and the tubular contact member 110 to each other, the paste-like solder 128 is disposed on the multi-layered substrate 120 and the tubular contact member 110 is placed on the solder 128 to be heated in a reflow furnace. In this case, generation of voids in the solder 128 is prevented by decreasing the pressure in the reflow furnace to remove gas present in the solder 128. When the pressure in the reflow furnace is decreased, however, the solder 128 may spatter when the gases present in the solder 128 expand. As a result, the solder 128 climbs up the inner wall 110c of the main body tube portion 101 from the first open end 110a to the second open end 110b (an insertion opening of the external electrode terminal 125) of the tubular contact member 110 and the solder 128 may remain on the inner wall 110c of the main body tube portion 101 in a state, for example, where the solder 128 does not smoothly spread out but is substantially hardened in a thick form.
When the solder 128 climbs up, as depicted in FIG. 11A, the external electrode terminal 125 cannot be inserted to a position deeper (toward the conductive plate 122) than solder 128a adhering to the inner wall 110c of the main body tube portion 101. When the external electrode terminal 125 is inserted, a load is applied to the external electrode terminal 125 at a point where the solder 128a adheres of the inner wall 110c of the main body tube portion 101. As depicted in FIG. 11B, the external electrode terminal 125 may thereby be bent or broken. Alternatively, the solder 128 bonding the main body tube portion 101 and the conductive plate 122 to each other may be broken and the main body tube portion 101 may become detached from the conductive plate 122 by insertion of the external electrode terminal 125 when the solder 128a has adhered to the inner wall 110c of the main body tube portion 101. The external electrode terminal 125 tends to drop off from the tubular contact member 110. Defective connection may therefore occur between the semiconductor chip 124 and the external electrode terminal 125.